Method of propulsion using solid propellant compositions



United States Patent M 3,098,351 METHUD 0F PROPULSION USING SOLE PROPELLANT COMPOSITIONS Horace M. Higgins and Calvin A. Gongwer, Glendora, Cahfl, assignors to Aerojet-General Corporation, Azusa, Calif., a corporation of Ohio No Drawing. Filed Feb. 18, 1955, Ser. No. 489,731 Claims. (Cl. 60-354) This invention relates to solid propellants useful for underwater jet propulsion and has for its object to improve the burning rates and properties of such propellants.

At the present time, propellant compositions employed for propelling underwater projectiles, are ordinarily intimate mixtures of finely divided inorganic oxidizing salts, such as chlorate, perchlorate, chromate or dichromate salts, dispersed in a finely divided reducing metal.

These propellant compositions are particularly adapted for military uses since they produce only condensable gases upon combustion. Such gases do not create the undesirable visible wake characteristics of other fuels heretofore in use. Such propellants, due to their compactness and non-gassing properties, also find valuable use in burning and cutting metals such as pipe in oil wells. Unfortunately, the combustion of such propellants is unstable at high pressures thereby severly limiting the conditions under which the propellants may be used for underwater propulsion or for cutting purposes.

In underwater operation the propellants are burned in the presence of water and a driving thrust is created by means of evaporating the water to steam. The magnitude of thrust is dependent upon the amount of heat available for heating water during the time the projectile is in motion and the amount of available heat is in turn dependent upon the properties of the particular propellant being burned as well as the amount of the propellant consumed. In underwater projectiles, the burning area of a propellant is confined to a given cross section, due to space limitations inherent in the design of such projectiles, thus, in order to increase the thrust created by burning such a propellant, it is necessary to increase its linear burning rate.

We have now found that the pressure stability during combustion as well as the burning rate of such propellants is greatly increased and improved by incorporating finely divided metal oxides into the propellant composition.

In accordance with the present invention we incorporate into the propellant compositions, oxides of the metals of periodic groups IVB, VB, VIB, VIIB and VIII and combined oxides and mixtures thereof. Catalysts which have been found to be particularly valuable are oxides such as chromium, manganese, cobalt, iron and nickel oxide, mixtures thereof, and combined oxides of these metals such as cobalt chromate. These compounds, in amounts of as little as 1% by weight of the propellant, substantially increase the linear burning rate of the propellants, and greatly improve their pressure stability during combustion.

The burning rate acceleration catalysts are incorporated into the propellant by mixing the finely divided ingredients, until an intimate and uniform mixture is obtained. Optimum results are achieved when the additives are employed in amounts of from about 1% to about 30% by weight of the propellant, and the reducing metal and inorganic oxidizing salt are in approximately stoichiometric proportions.

The reducing metals employed in the propellant composition are generally those of periodic groups IA, IIA, 11B and IIIB exhibiting electrode potentials of sufiicient magnitude to displace hydrogen from acids. Among the metals commonly used are: lithium, rubidium, potassium, sodium, caesium, strontium, barium, calcium, beryllium, magnesium, zinc, cadmium, and aluminum as well as alloys and mixtures of these metals.

Patented July 23, 1963 Table I By Wt,

Components Percent Propellant Sodiumperchlorate- Sodium perchlorate G Aluminum Potassium perchlorate H Beryllium Lithium perchlorate I Zinc Potassium permanganate..-

I Cadmium Sodium dichrornate To illustrate the effect of the additives of this invention upon such propellants, the results obtained by incorporating appropriate oxides into propellant G, comprising an intimate mixture of stoichiometric amounts of finely divided aluminum and potassium perchlorate, are presented in Table II.

Pressure stability refers to the pressures below which combustion is stable.

As shown by the data presented in Table II, the additives of this invention more than doubled the linear burning rate of the propellant in most cases, permitting greater consumption of fuel over a given period of time, hence creating greater thrust. In addition, as shown in column 5, a substantial increase in pressure stability, permitting a broader range of operating conditions, was attained. We have also found that two or more oxides may be used to obtain any particular balance of pressure stability and burning rate desired.

Similar results are obtained when the valuable addit-ives of this invention are incorporated into the other propellants described in Table I.

It is apparent from the above discussion that by incorporating the additives of this invention into propellant compositions containing a reducing metal and inorganic oxidizing salts, that propellant compositions are produced which provide greater thrust when used for underwater propulsion. The propellants of this invention are particularly suited for use in underwater propulsion plants of the type disclosed in assignees copending application Serial Nov 428,698, filed May 10, 1954, now abandoned. In addition, these propellants can be used under a wide range of pressures, thus greatly increasing their usefulness both for underwater propulsion and fior burning and cutting operations in oil wells.

We claim:

1. In a method of producing thrust for propulsion by burning a solid propellant composition, consisting essentially of an intimate mixture of a reducing metal selected from the group consisting of the metals of Periodic Groups IA, HA, and HE exhibiting electrode potentials of suflicient magnitude to displace hydrogen from acids, and an inorganic oxidizing salt in essentially stoichiometric proportions; the improvement which comprises combusting said propellant in the presence of a burning rate acceleration catalyst selected from the group consisting of the oxides of nickel and cobalt and mixtures thereof.

2. The method of claim 1 wherein the burning rate acceleration catalyst is oxide of cobalt.

3. The method of claim 1 wherein the burning rate acceleration catalyst is oxide of nickel.

4. The method of claim 1 wherein the inorganic oxidizing salt is selected from the group consisting of the chlorates, perchlorates, chromates, dichromates and permanganate salts of alkali and alkaline earth metals.

5. The method of claim 4 wherein the burning rate acceleration catalyst is present in amounts of from about 1% to about 30% by Weight of the total propellant composition.

6. A solid propellant composition consisting esesntially of an intimate mixture of a reducing metal selected from the group consisting of the metals of Periodic Groups IA, HA, and HE exhibiting electrode potentials of suflicient magnitude to displace hydrogen from acids, and an inorganic oxidizing salt, in essentially stoichiometric proportions and a burning rate acceleration catalyst selected from the group consisting of oxides of nickel and cobalt and mixtures thereof, in an amount of from about 1% 4 to about 30% by Weight of the total propellant composition.

7. A solid propellant composition consisting essentially of an intimate mixture of a reducing metal selected from the group consisting of lithium, rubidium, potassium, sodium, caesium, strontium, barium, calcium, beryllium, magnesium, zinc, cadmium and aluminum, and an inorganic oxidizing salt selected from the group consisting of chlorates, perchlorates, chromates, dichromates, and permanganates of alkali and alkaline earth metals in essentially stoichiometric proportions, and a burning rate acceleration catalyst selected from the group consisting of the oxides of nickel and cobalt and mixtures thereof.

8. The solid propellant composition according to claim 7 wherein the burning rate acceleration catalyst is present in amounts of from about 1% to about 30% by Weight of the total propellant composition.

9. A solid propellant composition consisting essential-1y of an intimate mixture of aluminum metal, and an alkali metal perchlorate in essentially stoichiometric proportions and cobalt oxide.

10. A solid propellant composition consisting essentially of an intimate mixture of aluminum metal, and an alkali metal perchlorate in essentially stoichiometric proportions and nickel oxide.

References Cited in the file of this patent UNITED STATES PATENTS 991,057 Grilling May 2, 1911 1,966,652 Tanner July 17, 1934 2,477,549 Van Loenen July 26, 1949 FOREIGN PATENTS 435,588 Great Britain Sept. 24, 1935 69,697 Holland Mar. 15, 1952 

1. IN A METHOD OF PRODUCING THRUST FOR PROPULSION BY BURNING A SOLID PROPELLENT COMPOSITION, CONSISTING ESSENTIALLY OF AN INTIMATE MIXTURE OF A REDUCING METAL SELECTED FROM THE GROUP CONSISTING OF METALS OF PERIODIC GROUPS IA, IIA, AND IIB EXHIBITING ELECTRODE POTENTIALS OF SUFFICIENT MAGNITUDE TO DISPLACE HYDROGEN FROM ACIDS, AND AN INORGANIC OXIDIZING SALT IN ESSENTIALLY STOICHIOMETRIC PROPORTIONS; THE IMPROVEMENT WHICH COMPRISES COMBUSTION SSID PROPELLANT IN THE PRESENCE OF A BURNING RATE ACCELERATION CATALYST SELECTED FROM THE GROUP CONSISTING OF THE OXIDES OF NICKEL AND COBALT AND MIXTURES THEREOF. 